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  <title>指数表达式</title>
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 <body class="docs"><div id="layout">
  <div id="layout-content"><div id="function.pow" class="refentry">
   <div class="refnamediv">
    <h1 class="refname">pow</h1>
    <p class="verinfo">(PHP 4, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">pow</span> &mdash; <span class="dc-title">指数表达式</span></p>

   </div>
 <div class="refsect1 description" id="refsect1-function.pow-description">
  <h3 class="title">说明</h3>
   <div class="methodsynopsis dc-description">
    <span class="methodname"><strong>pow</strong></span>
     ( <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.number" class="type number">number</a></span> <code class="parameter">$base</code></span>
    , <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.number" class="type number">number</a></span> <code class="parameter">$exp</code></span>
    ) : <span class="type"><a href="language.pseudo-types.html#language.types.number" class="type number">number</a></span></div>

    <p class="para rdfs-comment">
     返回 <code class="parameter">base</code> 的
     <code class="parameter">exp</code> 次方的幂。如果可能，本函数会返回
     <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>。
    </p>
   </div>

   
    <div class="refsect1 parameters" id="refsect1-function.pow-parameters">
  <h3 class="title">参数</h3>
  <p class="para">
   <dl>

    
     <dt>
<code class="parameter">base</code></dt>

     <dd>

      <p class="para">
       The base to use
      </p>
     </dd>

    
    
     <dt>
<code class="parameter">exp</code></dt>

     <dd>

      <p class="para">
       指数
      </p>
     </dd>

    
   </dl>

  </p>
 </div>

 <div class="refsect1 returnvalues" id="refsect1-function.pow-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
     <code class="parameter">base</code> 的
     <code class="parameter">exp</code> 次方的幂。
   If both arguments are non-negative integers and the result can be represented
   as an integer, the result will be returned with <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> type,
   otherwise it will be returned as a <span class="type"><a href="language.types.float.html" class="type float">float</a></span>.
  </p>
 </div>

 <div class="refsect1 changelog" id="refsect1-function.pow-changelog">
  <h3 class="title">更新日志</h3>
  <p class="para">
   <table class="doctable informaltable">
    
     <thead>
      <tr>
       <th>版本</th>
       <th>说明</th>
      </tr>

     </thead>

     <tbody class="tbody">
      <tr>
       <td>4.2.0</td>
       <td>
        如果不能计算幂，将发出一条警告，<span class="function"><strong>pow()</strong></span> 将返回 <strong><code>FALSE</code></strong>。<span class="function"><strong>pow()</strong></span> 开始不产生任何的警告。
       </td>
      </tr>

      <tr>
       <td>4.0.6</td>
       <td>
       如果可能函数现在会返回 <span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span> 的结果，之前
  总是返回 <span class="type"><a href="language.types.float.html" class="type float">float</a></span>，For older
        versions, you may receive a bogus result for complex numbers.
       </td>
      </tr>

     </tbody>
    
   </table>

  </p>
 </div>

 <div class="refsect1 examples" id="refsect1-function.pow-examples">
  <h3 class="title">范例</h3>
  <p class="para">
   <div class="example" id="example-4139">
    <p><strong>Example #1 <span class="function"><strong>pow()</strong></span> 的一些例子</strong></p>
    <div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /><br />var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">pow</span><span style="color: #007700">(</span><span style="color: #0000BB">2</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">8</span><span style="color: #007700">));&nbsp;</span><span style="color: #FF8000">//&nbsp;int(256)<br /></span><span style="color: #007700">echo&nbsp;</span><span style="color: #0000BB">pow</span><span style="color: #007700">(-</span><span style="color: #0000BB">1</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">20</span><span style="color: #007700">);&nbsp;</span><span style="color: #FF8000">//&nbsp;1<br /></span><span style="color: #007700">echo&nbsp;</span><span style="color: #0000BB">pow</span><span style="color: #007700">(</span><span style="color: #0000BB">0</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">0</span><span style="color: #007700">);&nbsp;</span><span style="color: #FF8000">//&nbsp;1<br /><br /></span><span style="color: #007700">echo&nbsp;</span><span style="color: #0000BB">pow</span><span style="color: #007700">(-</span><span style="color: #0000BB">1</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">5.5</span><span style="color: #007700">);&nbsp;</span><span style="color: #FF8000">//&nbsp;PHP&nbsp;&gt;4.0.6&nbsp;&nbsp;NAN<br /></span><span style="color: #007700">echo&nbsp;</span><span style="color: #0000BB">pow</span><span style="color: #007700">(-</span><span style="color: #0000BB">1</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">5.5</span><span style="color: #007700">);&nbsp;</span><span style="color: #FF8000">//&nbsp;PHP&nbsp;&lt;=4.0.6&nbsp;1.#IND<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</pre></div>
    </div>

   </div>
  </p>
 </div>


 <div class="refsect1 notes" id="refsect1-function.pow-notes">
  <h3 class="title">注释</h3>
  <blockquote class="note"><p><strong class="note">Note</strong>: 
   <p class="para">
    本函数会转换所有输入为数字，即使是非标量值，会导致怪异的（<em>weird</em>）结果。
   </p>
  </p></blockquote>
 </div>


 <div class="refsect1 seealso" id="refsect1-function.pow-seealso">
  <h3 class="title">参见</h3>
  <p class="para">
   <ul class="simplelist">
    <li class="member"><span class="function"><a href="exp.html" class="function" rel="rdfs-seeAlso">exp()</a> - 计算 e 的指数</span></li>
    <li class="member"><span class="function"><a href="sqrt.html" class="function" rel="rdfs-seeAlso">sqrt()</a> - 平方根</span></li>
    <li class="member"><span class="function"><a href="bcpow.html" class="function" rel="rdfs-seeAlso">bcpow()</a> - 任意精度数字的乘方</span></li>
    <li class="member"><span class="function"><a href="gmp_pow.html" class="function" rel="rdfs-seeAlso">gmp_pow()</a> - Raise number into power</span></li>
   </ul>
  </p>
 </div>

   
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